1. Field of the Invention
The present invention relates to an optical element holder for holding, e.g., a diffraction grating or other optical element. The invention also relates to an optical pickup provided with such an optical element holder.
2. Description of Related Art
In the conventional art, diffraction gratings for splitting light emitted from a light source are occasionally arranged in optical pickup optical systems (see, for example, Japanese Patent No. 3263569 and JP-A-2006-260678). Due to the presence of the diffraction grating, it becomes possible to employ, for example, a three-beam method, differential push-pull (DPP) method, or other method to generate a tracking error signal.
In a typical configuration, the diffraction grating is fixed to a base (optical stage) of the optical pickup once a rotational adjustment has been performed to bring the positions of a plurality of spots of light formed on an optical disk to target positions.
Blu-Ray (BD) disks and other optical disks on which large volumes of information can be recorded have recently become commercially viable, and currently, most diffraction gratings provided to BD-compatible optical pickups are made of glass instead of plastics. Where a diffraction grating is formed of glass, limitations imposed by the shape thereof make it difficult to rotate the diffraction grating. For this reason, it is typical for rotational adjustment of the diffraction grating to be performed by holding the diffraction grating in a holder (optical element holder), and causing the holder to rotate, as shown in Japanese Patent No. 3263569 and JP-A-2006-260678.
There shall now be given a description of a configuration example of the conventional art where a diffraction grating is held in a holder and attached to a base of an optical pickup. FIG. 10 is a schematic perspective view showing a diffraction grating prior to attachment to a base in a conventional art optical pickup. FIG. 11 is a schematic perspective view showing a diffraction grating attached to a base in a conventional art optical pickup.
As shown in FIG. 10, in the conventional art optical pickup, a substantially cylindrical holder 102 made of resin is employed as the holder for holding a diffraction grating 101. The diffraction grating 101 is anchored in a substantially central section of the holder 102 using an adhesive or the like. The holder 102 holding the diffraction grating 101 is housed within a hollow, substantially cylindrical housing space 103a provided to a base 103 of the optical pickup.
As shown in FIG. 11, the holder 102 housed within the housing space 103a is pressed against an abutment face 103b of the base 103 by a spring 104 arranged on the reverse side of the holder 102 (see FIG. 10). Specifically, the holder 102 is held accommodated within the housing space 103a through the action of the spring 104. However, as mentioned previously, the diffraction grating 101 must be rotationally adjusted. For this reason, the urging force of the spring 104 is adjusted so that that rotational adjustment may be performed with the holder 102 pressing against the abutment face 103b. 
As shown in FIG. 10, an adjustment slot 102a into which an adjustment tool is inserted is formed in the holder 102. As shown in FIGS. 10 and 11, a cutout 103c into which an adjustment tool is inserted is formed in the optical pickup base 103. For this reason, rotational adjustment of the holder 102 housed within the housing space 103a and pressed against the abutment face 103b by the spring 104 may be performed using an adjustment tool. Once rotational adjustment has been performed using the adjustment tool, the holder 102 is fixed in an immobilized manner to the base 103 using an adhesive or the like. Fixing the holder 102 using an adhesive or the like thus completes the task of attaching the diffraction grating 101 to the base 103.